Plastics stabilized against ultraviolet radiation

It is already known that plastics, for example polyolefines, are attacked and gradually destroyed by the action of ultraviolet radiation, for example ultraviolet radiation of the sunlight. In order to reduce this destruction, so-called inhibitors or stabilizers are added to the plastics.

The present invention therefore provides plastics stabilized against ultraviolet radiation and containing as stabilizer a compound of the formula ##EQU2## wherein X represents an oxygen or sulfur atom, R 1 and R 2 are either β-cyanoethyl radicals or have the same definition as R 3 , R 3 represents a hydroxyalkyl or a hydroxyalkylphenyl group, the phenyl radical of the latter being optionally substituted by one or more halogen atoms, or a halogenoalkyl carbalkoxyalkyl, acyloxyalkyl or cyanoalkyl group the alkyl radical of which has from 1 to 6 carbon atoms.

The tertiary phosphine oxides to be used according to the invention can be prepared by various known methods, for example by hydrolysis of phosphine dihalides or quaternary phosphonium compounds, by Michael's-Arbusov's-reaction from phosphinous acid esters, or most simply by direct oxidation of the corresponding tertiary phosphines.

The tertiary phosphine sulfides to be used according to the invention can be easily prepared by the addition of elementary sulfur on the corresponding tertiary phosphines according to known methods. Suitable tertiary phosphine oxides are for example bis-(2-cyanoethyl)-hydroxymethyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxyethyl-phosphine oxide, bis-(2-cyanoethyl)-2-chloro-1-hydroxyethyl-phosphine oxide, bis-(2-cyanoethyl)-2,2,2-trichloro-1hydroxyethyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxycyclohexyl-phosphine oxide, bis-(2-cyanoethyl)-2-carboxymethylethyl-phosphine oxide, bis-(2-cyanoethyl)-1,2-dicarboxymethylethyl-phosphine oxide, bis-(2-cyanoethyl)-2,2-dichloro-1-hydroxy-ethyl-phosphine oxide, bis-(2-cyanoethyl)-bis-chloromethyl-hydroxy-methyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxy-2-phenyl-ethyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxyl-1-phenyl-2-chloro-ethyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxy-1-phenyl-ethyl-phosphine oxide, bis-(2-cyanoethyl)-1-hydroxy-1-(4-bromophenyl)-ethyl-phosphine oxide, bis-(2-cyanoethyl)-hydroxy-(2,4-dichlorophenyl)-methyl-phosphine oxide.

Tris-chloromethyl-phosphine oxide, oxethylated tris-hydroxymethyl-phosphine oxide, tris-hydroxymethyl-phosphine oxide, oxpropylated tris-hydroxymethyl-phosphine oxide, tris-(2-cyanoethyl)-phosphine oxide, tris-acetoxymethyl-phosphine oxide, tris-stearoyloxymethyl-phosphine oxide, tris-benzoyloxymethyl-phosphine oxide, tris-(2-carbethoxy)-ethyl-phosphine oxide, tris-(1-hydroxy-2-chloro-ethyl)-phosphine oxide, tris-(1-hydroxy-1-phenyl-ethyl)-phosphine oxide.

Suitable tertiary phosphine sulfides are, for example, tris-hydroxymethyl-phosphine sulfide, tris-(2-cyanoethyl)-phosphine sulfide, tris-stearoyloxy-methyl-phosphine sulfide, tris-(2-carbomethoxy)-ethyl-phosphine sulfide, bis-(2-cyanoethyl)-hydroxymethyl-phosphine sulfide. The compounds to be used according to the invention are especially suitable as stabilizers against ultraviolet radiation for polyethylene, polypropylene, polybutene, poly-(4-methyl-1-pentene), copolymers of these substances as well as for polystyrene.

They are added to the polymers in an amount of 0.1 to 5 % by weight, preferably of 0.5 to 2 % by weight.

They may be incorporated into the polymer in the usual manner, for example by mixing, kneading or grinding. In this process it may also be advantageous to use mixtures of the additives.

Moreover, further components, such as pigments, lubricants, fillers or antistatic agents may be added to the plastics. In most applications, it can also be desirable to use antioxidants, for example of thiodipropionic acid or distearyl sulfide type and/or antioxidants corresponding to the general formulae ##SPC1##

wherein

n=O-6

R 1 = alkyl having from 1 to 20 C-atoms

R 2 = alkyl having from 1 to 6 C-atoms

The compounds of the invention differ from known UV-absorbers containing hydroxyl groups in not being colored, even after exposure to ultraviolet light, as well as in their partly better stabilizer properties.

The invention is illustrated by the following examples.

EXAMPLES 1- 13

100 Parts of polypropylene stabilized with 0.1 % of 2,2-isopropylidene-bis-(4-isononylphenol) and 0.25 % of thiodipropionic acid lauryl ester are mixed with one part of the additives mentioned below in a kneader-mixer provided with heating means at a temperature of 200°C.

In order to determine the stabilizing effect under the action of ultraviolet light, the brittle time of sheets mounted on an aluminium foil and having a thickness of 100 μ is measured by means of the Xenon test apparatus 450 of the Cassella system, manufactured by Messrs. Heraeus at Hanau (W. Germany); it is the time after which the test sheet exhibits a clod-like rupture by pulling a cotton thread imbedded therein.

The results are summarized in the following table.

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stabilizer brittle time

color after exposure to

No. (hours)

ultra-violet radiation

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1 bis-(2-cyanoethyl)-hydroxymethyl-

910 colorless

phosphine oxide

2 bis-(2-cyanoethyl)-1-hydroxy-

850 colorless

ethyl-phosphine oxide

3 bis-(2-cyanoethyl)-2-chloro-1-

860 faintly yellow

hydroxyethyl-phosphine oxide

4 bis-(2-cyanoethyl)-2,2,2-tri-

780 faintly yellow

chloro-1-hydroxyethyl-phosphine oxide

5 bis-(2-cyanoethyl)-1,2-dicarboxy-

910 colorless

methylethyl-phosphine oxide

6 tris-hydroxymethyl-phosphine oxide

1025 colorless

7 oxethylated tris-hydroxymethyl-phos-

1280 colorless

phine oxide

8 oxpropylated tris-hydroxymethyl-

830 colorless

phosphine oxide

9 tris-2-(cyanoethyl)-phosphine sulfide

1125 colorless

10 tris-stearoyloxymethyl-phosphine sul-

880 colorless

fide

11 tris-(2-carbmethoxy)-ethyl-phos-

810 colorless

phine sulfide

12 comparative experiment without an additive

162

13 2-(2'-hydroxy-3', 5'-di-tert.-

920 yellow

butylphenyl)-5-chloro-benzotriazole

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